BCH 471

 Also called packed cell volume (PCV).  Its determination is part of the daily routine in hematological laboratories.  It is used as a simple screening test for anemia and is used in conjunction with the mean cell volume (MCV) and mean cell haemoglobin concentration (MCHC).  MCV: is a measure of the average RBC size  MCHC: is a measure of the concentration of hemoglobin in a given volume of packed red blood cells. ◦ It is calculated by dividing the hemoglobin by the HCT.

1- The blood of a colleague may be taken in a heparinised capillary tube or a blood sample in such a tube may be used which has been taken not more than 6 hours before and stored at 4°C. 2- Seal the dry end of the tube, and centrifuge for 5 min. 3- The column of red cells will be seen, topped by the grayish- red layer of leukocytes and above this a thin creamy layer of platelets, the “Buffy coat”. 4- Measure the length of the column of red blood cells (A), and the total length of blood components (B). HCT= A/B

 Normal Range ◦ Men 0.40 – 0.54 ◦ Women 0.37 – 0.47  Low hematocrit may be due to: ◦ Anemia ◦ Bleeding ◦ Destruction of red blood cells ◦ Leukemia ◦ Nutritional deficiencies of iron, folate, vitamin B12, and vitamin B6 ◦ Overhydration  High hematocrit may be due to: ◦ Polycythemia ◦ Dehydration ◦ Low blood oxygen levels (hypoxia)

 ESR is the rate at which erythrocytes settle out of anticoagulated blood in 1 hour.  ESR is used clinically as a non-specific screening test to detect the presence of infection in the body in general. It is used as well as a means of monitoring the status of chronic inflammatory disease such as rheumatoid arthritis.  ESR is not diagnostic of any particular disease, but rather is an indication that a disease process is ongoing and must be investigated.

 This test is based on the fact that inflammatory and necrotic processes cause an alteration in blood proteins, resulting in an aggregation of red cells, which make them heavier and more likely to fall rapidly when placed in a special vertical tube.  ESR is dependent on the plasma concentration of asymmetric macromolecules such as globulins, fibrinogen, besides the concentration of red cells.

 In this technique, cells are allowed to sediment under the effect of gravity, using a Westergren’s tube.  Draw the blood up into a Westergren’s tube exactly to the zero mark. The tube is placed upright in the rack and left undisturbed.  The length of the column of clear plasma at the top is noted at the end of 1 hour and again at he end of 2 hours.